Hand held, reciprocating power tools such as saws are known in which a wobble mechanism translates rotary motion of a motor shaft into reciprocating linear motion of a plunger. A saw blade is attached to one end of the plunger.
U.S. Pat. No. 3,945,120 issued to Ritz discloses improvements in hand-held, electric motor driven so called "all purpose" reciprocating saws. In Ritz, a reciprocating saw is provided which produces an orbital blade action. With this action there is a generally forward or "pushing" component for returning the blade to the cutting position, and a generally rearward or "pulling" component to perform cutting. The orbital movement is designed to generate more force in the cutting stroke to better cut wood.
The purpose of the Ritz device is to provide a plurality of angular stroke patterns to adjust the degree of orbital movement of the saw blade. A disadvantage in Ritz is that the linear cutting stroke length is constant.
Another disadvantage in Ritz is that two axes are required to provide a wobble motion. The first axis of the Ritz wobble mechanism, embodied in a wobble drive shaft, for providing linear reciprocation, has a fixed axial orientation and is not adjustable. The second axis of the Ritz wobble mechanism is an eccentric shaft which is transverse to the wobble drive shaft and provides the orbital component of the blade motion. The reciprocating motion of a plunger bearing the blade must be coordinated with the plunger's orbital movement. In Ritz, when the direction of the motor is reversed, the only effect occurs in the eccentric shaft, not in the wobble drive shaft. In this manner, the orbital stroke is varied.
U.S. Pat. No. 5,555,626 to Fuchs also discloses a reciprocating tool drive mechanism with a two part orbital movement. A wobble arm is used to drive the plunger of a power tool. An eccentric, axially-oriented with the wobble arm, provides the orbital movement.
Fuchs does not disclose or suggest adjusting the cutting stroke length. In contrast, Fuchs provides an orbital motion that is only manually adjustable, and the wobble angle is not adjustable at all.
In using reciprocating saws, a short stroke length is desirable for a slower cut, such as in plumbing and electrical work, where precision of the cut is critical. A long stroke length is useful for a fast cut, such as in cutting wood or in building or renovating work, where speed is more desirable than precision.
Thus, there is a need for a reciprocating saw which incorporates a drive system providing linear reciprocating motion. There is also a need for a reciprocating saw that provides an adjustable cutting stroke mechanism. Thus, one product may be used in a variety of work applications.
Therefore, it is an object of the present invention to provide a motorized tool incorporating a drive system providing linear reciprocating motion which can be used to provide both shorter, precise stroke lengths, as well as longer stroke lengths.
Another object of the present invention is the provision of a drive system for a motorized tool which generates a multi-stroke reciprocating motion about a single axis.